The present invention may be used in the treatment and prophylaxis of gastrointestinal diseases caused by a range of organisms including E. coli, Salmonella, Campylobacter, Helicobacter, Vibrio, Shigella, Yersinia and Aeromonas bacteria. For the purposes of exposition, however, the invention will be explained in its application to enterotoxigenic E. coli (ETEC) in humans. It will be understood however that the broadest part of the invention is not limited by this exemplary application.
Diarrhoea caused by enterotoxigenic E. coli (ETEC) causes significant discomfort in adults and can lead to death through dehydration of young and older people. A significant fraction of the diarrhoea suffered by travellers to destinations such as Mexico, Africa and South-East Asia is caused by ETEC.
One treatment currently used for travellers' diarrhoea is prophylactic antibiotic therapy, for example with Amoxycillin. However antibiotic resistance has reduced the effectiveness of antibiotic therapy and side-effects such as constipation or diarrhoea are common.
Symptomatic therapy is used for vomiting and diarrhoea, for example with loperamide hydrochloride, atropine sulphate and diphenoxylate hydrochloride. However the inappropriate use of Loperamide and Atropine leads to severe constipation and the inappropriate use of diphenoxylate may lead to dependence. These agents are also unsuitable for administration to children.
A further treatment includes fluid replacement therapy using isotonic drinks. However fluid replacement therapy is merely palliative, and does not decrease clinical diarrhoea
Furthermore symptomatic relief and fluid therapy will treat the symptoms but will not remove the cause.
Milk and egg products have been shown to have potential therapeutic and preventative roles in the relief of symptoms of gastrointestinal disorders
Peterson and Campbell in U.S. Pat. No. 3,376,198 teach the immunisation of milk-producing ungulates to produce antibodies or “protective principles” against bacteria and viruses.
Carlander et al in BioDrugs 2002; 16(6):433-7 teach the use of antibodies derived from egg yolk to decrease Pasteurella bacteria in the opening of the gastrointestinal tract (the mouth).
Shimamoto et al in Hepatogastroenterology 2002 49(45): 709-714 teaches the use of specific antibodies against Helicobacter pylori raised in eggs to decrease the number of H. pylori bacteria in the stomach of patients.
Linggood et al in U.S. Pat. No. 4,971,794 teach the use of hyperimmune bovine colostrum as a source of antibodies to E. coli. The cows were vaccinated using preparations of pili from a mixture of strains. The patent teaches that the vaccine must comprise antigens of a plurality of strains of E. coli expressing Type 1 pili, CFA 1 pili, CFA 2 pili and K88 pili. K88 is associated with porcine ETEC.
Hastings in U.S. Pat. No. 5,017,372 teaches the use of hyperimmune colostrum from ungulates as a source of antibodies to E. coli. The ungulate vaccine was made using the following method: Various E. coli bacteria were grown under conditions so that CFA 1 or CFA 2 or both were produced. The bacteria were then lysed by ultrasound to release these antigens and heat labile toxins.
Freedman et al in The Journal of Infectious Diseases 1998, 177:662-7 teaches the use of hyperimmune colostrum as a source of antibodies against E. coli. A vaccine was made by growing bacteria strains in a broth designed to optimise CFA expression, then purifying the CFA using precipitation followed by size-exclusion or ion exchange chromatography.
Tackett et al in The New England Journal of Medicine May 12, 1988 pp 1240-1243 describe the pooling of multiple inactivated (formaldehyde or glutaraldehyde treated) bacterial whole cell suspension in a vaccine administered to cattle. The whole-cell suspensions comprise E. coli of O serogroups: O6, O8, O15, O20, O25, O27, O63, O78, O114, O115, O128, O148, O153 and O159 as well as heat-labile enterotoxins, cholera toxin, CFA 1 and E. coli surface antigen 3. O antigens of E. coli such as O6, O8, O15, O20, O25, O27, O63, O78, O114, O115, O128, O148, O153 and O159 are heat stable antigens located on the bacterial cell wall and not on protruding structures such as pili (fimbriae) or flagella. These O antigens are composed of polysaccharide moieties linked to a core lipooligosaccharide complex common to the wall material of most Gram negative bacteria. Because of the close association between the O antigens and the cell wall, O antigen based vaccines have been made from cell walls or whole inactivated bacteria. The lipopolysaccharide endotoxins are a normal part of the outer cell wall of the bacteria and their toxic regions are embedded in the cell wall (see “Endotoxins in Health and Disease”, 1999 Chapter 12 and other chapters). A further reason for the fact that normal veterinary practice uses whole cell bacterial antigens rather than individual O antigen moieties is that O antigens are endotoxins—the use of high concentrations of endotoxins in pregnant cattle is considered problematic in prior art in terms of animal welfare and productivity.
The use of milk and egg products in the prior art for the prevention of symptoms of gastrointestinal disorders is associated with a number of problems.
Cholera toxin (see Tackeft et al., 1988) are likely to be difficult to register because of their high toxicity. Further, heat labile toxins, although highly immunogenic are not likely to be protective.
The extent of protection obtained from antibodies produced as above is unsatisfactory. One of the attendant problems is that large quantities of immune concentrate are needed to produce a satisfactory prophylactic outcome. When whole cell antigens are used, an enormous variety of antibody responses arise and assays for antibody titre are difficult to interpret. A key issue is whether a particular detected antibody is protective or not. Whole bacterial cells have many antigens that are unlikely to be related to protection. In addition, vaccines comprising Gram negative bacteria are more likely to produce adverse vaccine reactions and therefore present regulatory problems due to adverse animal ethics reports and therapeutic goods adverse reaction reports. Adverse vaccine reactions are likely to stop dairy farmers from participating in any production venture for milk antibodies.
The discussion of the background to the invention herein is included to explain the context of the invention. This is not to be taken as an admission that any of the material referred to was published, known or part of the common general knowledge in any country.